How accurate is a single cutpoint to identify high blood pressure in adolescents?

In 2007 the International Diabetes Federation (IDF) proposed single blood pressure (BP) cutpoints (systolic: ≥130 mm Hg and diastolic: ≥85 mm Hg) for the diagnosis of high blood pressure (HBP) in adolescents. Before this proposal, HBP had been defined as BP at or above the 95th percentile for age, sex, and height percentile (reference standard). In this study, we evaluated the risk for misclassification when using the IDF single-cutpoints criteria. We first applied the IDF criteria to a reconstructed population with the same age, sex, and height distribution as the population used to develop the reference standard. The proposed single cutpoints corresponded to percentiles from the 81.6th to 99.9th for systolic BP and from the 92.9th to 98.9th for diastolic BP in the reconstructed population. Using IDF criteria, there were high false-negative fractions for both systolic and diastolic BP (from 54% to 93%) in 10- to 12-year-olds and a false-positive fraction up to 35% in older subjects. We then applied the IDF criteria to 1,162 overweight/obese adolescents recruited during 1998-2000 from pediatric clinical centers in Milano, Varese, and Modena in Italy and in Zaragoza, Spain. Overall false-negative and false-positive fractions were 22% and 2%, respectively; negative predictive values were especially low for 10- to 12-year-old subjects. The use of IDF's single cutpoints carries a high risk of misclassification, mostly due to false negatives in younger subjects. The effort to simplify diagnosis could be overcome by the risk of undiagnosed HBP.